As urban areas become more populated and denser, stormwater management becomes an important matter. Since natural areas are becoming exploited and green areas in cities are removed the stormwater flow increases due to the conversion of impermeable surfaces into hard surface areas. The increase in stormwater flow can cause flooding if the pipeline system is insufficient.

Change in climate caused by anthropogenic emissions will expose our communities to difficult challenges. Urban flooding from sewers is one of them, and may become more frequent in parts of the world where precipitation is predicted to increase in the future. In order to develop our cities in a sustainable manner and create resilience, the urban drainage system has to be a part of this development. Many of the techniques related to sustainable urban drainage systems, like storage reservoirs and open channels, require access to land space. However, about 40-50 % of the impermeable surfaces in cities consist of roof. Consequently, an interesting alternative to decrease stormwater flow is green roof due to its ability to reduce and attenuate the flow.

The aim of this thesis is to demonstrate the benefits of green roof’s stormwater management through simulations in Mike Urban. The simulations are made over two neighborhoods in Karlstad with future climate changes. The simulations indicated that green roof in these neighborhoods show good potential to lower the risk of flooding and the numbers of flooded wells by a 10- and 2-year rain is decreased by 42 and 58 %.

There's a big demand for activated carbon in Ghana, it's used for the country's mining industry as well as in a multitude of other applications. Currently all activated carbon is imported despite the fact that the country has a large supply of agricultural waste that could be used for its production. This study focuses on activated carbon production from oil palm kernel shells from the nations palm oil industry.

Earlier research points to a set of specific conditions needed for the production. The pyrolysis process produces biochar from the biomass and the process is set to take place for 2 h at 600 °C after a initial heating of 10 °C/min. The activation process then produces the activated carbon from the biochar and is set to take place for 2 h at 850 °C with a heating rate of 11.6 °C/min.

Two reactors are designed to meet the desired conditions. The reactors are both set up to use secondary gases from diesel burners to heat the biomass. The heating is accomplished by leading the hot gases in an enclosure around a rotating steel drum that holds the biomass. To improve the ability to control the temperature profile in the biomass two outlet pipes are set up on top of the reactor, one above the biomass inlet and one above the biomass outlet. By controlling how much gas that flows to each outlet both the heating rate and the stability of the temperature profile can be controlled. The secondary gas inlet is set up facing downwards at the transition between the heating zone (area of initial heating) and the maintaining zone (area of constant temperature).

The two reactors are modeled the physics simulation software COMSOL Multiphysics. Reference operating parameters are established and these parameters, as well as parts of the design, are then changed to evaluate how the temperature profile in the biomass and biochar can be controlled. A goal area was set up for the profile in the biomass where it was required to maintain a temperature of between 571.5 and 628.5 °C after the initial heating to be seen as acceptable. Similarly a goal area was set for the biochar between 809 °C and 891 °C after the initial heating.

It's found from the simulations that the initial design of the reactors work well and can be used to produce the desired temperature profiles in the biomass and biochar. Furthermore it's concluded that the initial design for the pyrolysis reactor can be improved by having the gas outlet pipe situated by the biomass inlet face downwards instead of upwards. The redesign improves the overall efficiency of the reactor by increasing the heating rate and maintained temperature.

The evaluation of the operating parameters led to the conclusion that the secondary gas inlet temperature effects the temperature profile to a greater extent than the gas mass flow in both reactors thereby making them more energy efficient. The increase in efficiency comes with a drawback of more unstable temperature profile. If the temperature profile becomes too unstable it will include temperatures that are too high or too low to be seen as acceptable.

Härjeåns Energi AB in Sveg is a company consisting a brand-new cogeneration plant and a biofuel plant where the company produces pellets out of wooden sawdust. Before pelleting, the sawdust is stored in a large stack. However, the company had noted that the amount of sawdust delivered to the stack minus the sawdust taken from the stack for pelleting did not add up to the sawdust left in the stack. At some point during storage and handling of the sawdust large quantities has disappeared. The purpose of this study was to investigate how and when the dry matter losses occur and the magnitude of the losses regarding two things: the dry matter losses associated with storing of the sawdust and the dry matter losses related to the handling of the sawdust. The most important goal of this study, for the company, was to create an equation that describes the amount of dry matter losses that reasonably should have disappeared from the stack depending on for how long the sawdust has been stored. Simply to be able to make a write-off of the sawdust inventory balances on a regular basis. The purpose and goals were answered by conducting a literature study on the subject, studying the company’s sawdust accounts and their way of handling the sawdust, and also by constructing two simulation models of the dry matter losses in the stack of sawdust.

Dry matter losses resulting from the storage of biomass may occur through the decomposition mechanisms; respiration, biodegradation and thermal and chemical degradation. But the storage effect on fuel quality is complex. Time of storage, climatic conditions and the geometry and structure of the stacks are some factors that affect the change in biomass properties.

This degradation, along with how the company manages the sawdust, contributes to dry matter losses. However, the largest contributing factor to the dry matter losses is the storage part. Some contributing factors are the size of the stack, if it’s been compacted and if the sawdust is stored open without coverage. When the models were built it turned out that the result was well in line with what actually had disappeared in the stack, according to the sawdust inventory, during the investigated years 2013-2017.

For example, by reducing the maximum height of the stack to a maximum of 5-7 meters and apply the last-in-first-out-method on the spruce, while the pine can be stored for a longer time, would certainly contribute to reduced dry matter losses and, consequently, economic losses.

In the future, however, more resources should be invested in research about storing the fraction of sawdust, as well as storing wood in stacks larger than a maximum height of 5-7 meters. Today there are no research at all within these two categories, but if there were, it could facilitate many energy-producing companies.

In the household appliance industry, heat pump systems have been used for a long time in refrigerators and freezers to cool food, and the industry has driven the development of small, high-quality, low-price heat pump components. In the last few decades, heat pump systems have been introduced in other household appliances, with the express purpose of reducing electricity consumption. Heat pump tumble dryers have been on the market since 2000 and dominate the market today. A heat pump dishwasher was introduced on the market in 2014 and a heat pump washing machine in 2016. The purpose of adding a heat pump system in these three products was to decrease electricity consumption.

Papers I and II used a methodology where transient simulation models were developed and used to increase knowledge about how to decrease electricity consumption for a tumble dryer and a dishwasher by adding a heat pump system. Papers II to V showed that a lower electricity consumption and lower global warming potential together with an energy-efficient drying method, where no humid air evacuates to the kitchen, give a heat pump dishwasher competitive advantages compared to any conventional dishwasher currently on the market. Using simulations, this dissertation concludes that a future commercial heat pump dishwasher, using R600a as a refrigerant, will reduce electricity consumption and total equivalent warming impact (TEWI) by 50% compared to the conventional dishwasher.

The willingness from the customer chain to pay extra for this heat pump dishwasher is because of the decreases electricity consumption and the fact that no humid air evacuates to the kitchen. This willingness makes the heat pump dishwasher to a variant which have possibility to succeed on the future market.

The challenge for the manufacturer is to develop and produce a high-quality heat pump dishwasher with low electricity consumption, predict future willingness to pay for it, and launch it on the market at the right moment with the right promotion in order to succeed.

Historically, domestic tasks such as preparing food and washing and drying clothes and dishes were done by hand. In a modern home many of these chores are taken care of by machines such as washing machines, dishwashers and tumble dryers. When the first such machines came on the market customers were happy that they worked at all! Today, the costs of electricity and customers’ environmental awareness are high, so features such as low electricity, water and detergent use strongly influence which household machine the customer will buy. One way to achieve lower electricity usage for the tumble dryer and the dishwasher is to add a heat pump system.

The function of a heat pump system is to extract heat from a lower temperature source (heat source) and reject it to a higher temperature sink (heat sink) at a higher temperature level. Heat pump systems have been used for a long time in refrigerators and freezers, and that industry has driven the development of small, high quality, low price heat pump components. The low price of good quality heat pump components, along with an increased willingness to pay extra for lower electricity usage and environmental impact, make it possible to introduce heat pump systems in other household products.

However, there is a high risk of failure with new features. A number of household manufacturers no longer exist because they introduced poorly implemented new features, which resulted in low quality and product performance. A manufacturer must predict whether the future value of a feature is high enough for the customer chain to pay for it. The challenge for the manufacturer is to develop and produce a high-performance heat pump feature in a household product with high quality, predict future willingness to pay for it, and launch it at the right moment in order to succeed.

Tumble dryers with heat pump systems have been on the market since 2000. Paper I reports on the development of a transient simulation model of a commercial heat pump tumble dryer. The measured and simulated results were compared with good similarity. The influence of the size of the compressor and the condenser was investigated using the validated simulation model. The results from the simulation model show that increasing the cylinder volume of the compressor by 50% decreases the drying time by 14% without using more electricity.

Paper II is a concept study of adding a heat pump system to a dishwasher in order to decrease the total electricity usage. The dishwasher, dishware and water are heated by the condenser, and the evaporator absorbs the heat from a water tank. The majority of the heat transfer to the evaporator occurs when ice is generated in the water tank. An experimental setup and a transient simulation model of a heat pump dishwasher were developed. The simulation results show a 24% reduction in electricity use compared to a conventional dishwasher heated with an electric element. The simulation model was based on an experimental setup that was not optimised. During the study it became apparent that it is possible to decrease electricity usage even more with the next experimental setup.

In a heat pump dishwasher, the whole dishwasher with the cabinet, dishware and process water is the heat sink, while a water tank, whose contents will freeze, is the heat source. The aim of the experimental concept study presented here was to evaluate a new drying method for a heat pump dishwasher. In this method, the drying of the dishware occurs as a fan circulates humid air in a closed system in which the water on the dishware evaporates inside the warm dishwasher cabinet and then condenses on a cold surface of the frozen water tank. The evaluation of drying performance was based on the European standard EN50242, which considers visible water drops left on the dishware after a completed dishwashing cycle. The results showed that this new closed drying method was more energy efficient compared to an existing open drying method, and that the drying start temperature and the drying time had a significant effect on the drying performance. Its lower electricity consumption and the fact that it does not vent humid air into the kitchen gives this heat pump dishwasher a competitive advantage over dishwashers using an open drying method.

Electricity usage by a household dishwasher can be reduced by using a heat pump system to heat the dishwasher cabinet, dishware and washing water. The evaporator obtains the energy from an energy storage unit which consists of a container filled with water which freezes to ice. The majority of the heat transfer from the energy storage to the evaporator occurs when ice is created in the energy storage unit. A transient simulation model of a dishwasher with a heat pump system was developed and compared to an experimental setup with good agreement. A simulation study of the compressor cylinder volume and the compressor operating time was performed. The results showed a 24% reduction in total electricity use compared to a dishwasher cycle using a traditional electric element.

In a heat pump dishwasher, the dishware and the dishwater constitute the heat sink and a water tank filled with water, which can freeze, the heat source. A simulation model developed and validated earlier was modified and used in a parameter study to determine the lowest total electricity usage for the refrigerants R134a, R290, and R600a with different cylinder volumes of the compressor. The total equivalent warming impact (TEWI) was calculated in three regions with different CO2 eq. emissions from electricity generation, i.e., Sweden, Europe (OECD), and Europe (Non-OECD), for small, medium-sized, and large households. In regions with low CO2 eq. emissions from electricity generation, the total TEWI of a heat pump dishwasher is the lowest with R600a and the highest with R134a, and in regions with high CO2 eq. emissions, the total TEWI is the lowest with R600a and the highest with the conventional electrical element.

Spouted bed drying technology shows promising results for the drying of unscreened sawdust in superheated steam. In this paper, the experiences from designing, running and evaluating two spouted bed continuous feed dryers are presented. Stable running conditions and drying results have been achieved. This has been particularly important for sawdust that will be compressed into pellets or briquettes. The spouted bed superheated steam dryer also shows high potential for energy efficient integration into sawmills. Our recommendation is thus, to use the outlet steam temperature as the control parameter for the outlet moisture content. A drying rate above and one below the fibre saturation level, can be identified. Visual observations through the viewing glass in the drying zone in both the dryers clearly showed that not all of the material participated in the spout at all times; there were, however, no indications of dead zones. A heat transfer analysis indicated that only about 70% of the surface area of the material was in thermal contact with the steam. This paper sums up the experiences regarding drying properties, control and system properties obtained when sawdust is dried using superheated steam as the drying medium. Further work on standardised dryers in series or in parallel is necessary to increase the capacity in the spouted bed dryer.

Plastic is one of the most universal materials used today. With a good future view, with new implementations and applications, it makes a lot of time to look at the production and management of the plastic materials. Plastic materials that have been used in our daily lives cause serious environmental problems. Millions of tons of these non-degradable plastics accumulate in the environment every year. The basic problem is that plastic is not naturally occurring in nature since containers are usually made of polyethylene terephthalate. This means that microorganisms do not have the ability to break it down to the current cycle. It takes hundreds of years for plastic containers to break down, not biologically but only degenerate into smaller and smaller pieces. Plastic breaks down into smaller pieces that become smaller and smaller until we cannot see them with the naked eye, mainly through heat and UV light. Although we cannot see them, they are still present and become part of our nature forever. Bioplastics is the plastic industry's tool to try to reduce these little pieces of our nature that will remain forever so that they do not grow more. With today's plastic packaging, which is said to be bioplastic, additives of, for example, cobalt and nickel, which are said to make it easier for the polymers to break down over time, have proven to be not as effective as they thought.

Polyhydroxyalkanoates (PHA) are polymers which are biodegradable as based on their composition have different physical properties. PHA is a family of natural polyesters synthesized from various microorganisms discovered in 1926. Once discovered, interest has been high due to their biodegradability and its production from renewable resources. The polymers can be described generally as production from microorganisms under controlled conditions, where they occur naturally in organisms that classify them as biopolymers. Some of these polymers are already industrially produced on a large scale today. However, many still apply to several new areas but must be optimized for commercial production.

Biopolymers can be classified into four groups. Amino-acid-based polysaccharides from bacteria, polyphenol-based and polyesters that this study is looking at. Depending on what the microorganisms possess for character traits and what they give to the substrate to break down, it gives polyesters with different physical properties. This case is a short-chain polyester to be formed, more specifically P3HB which is a three-carbon PHB polyester in its polymer which can be up to 5-7 units long.

To avoid ongoing problems, a solution is needed. A solution that has received much attention to reduce plastic residues in nature is the use of biodegradable plastics and among them polyhydroxyalkanoates. Polyhydroxyalkanoates (PHAs) are common intracellular compounds found in bacteria, archaea and in few eukaryotes such as yeast and fungi. PHA acts as an energy storage polymer that is produced in some microorganisms when the carbon source is abundant and other nutrients such as nitrogen, phosphorus, oxygen or sulfur are limited. These polymers accumulate intracellularly up to 90% of the dry weight of the cell under nutritional conditions and act as energy saving materials. It has resembled mechanical properties like the traditional oil-based plastic such as polypropylene or polyethylene that can be formed with other synthetic polymers. PHA plastics possess many more applications, in agriculture, packaging and in the medical industry. It is biodegradable and also immunologically compatible. What the PHAs plaster can cause is an ultimate decomposition from a non-fossil source, which is exactly why it is very attractive.

The purpose of this study was that from a hypothesis see within a limited time frame of ten hours of bio sludge from Gruvön, Skoghall and Bäckhammar's use could accumulate PHA with the aid of added readily degradable substrate. The process of the study will be a small part of a current research project together with Paper Province, Promiko, Pöyry and RISE. The aim of their study is to use residues from the forest industry to make hydrogen as well as bioplastics. This study will help to look at a subprocess of their cascading process.

The aim of the study is to be able to measure the amount of PHA that could accumulate and rank the potential of the different uses. Using chemical analysis methods and extractions, it will provide opportunities to measure the accumulation of PHA in the various bacterial cultures of biomass from the use. The methods involve soxhlet extraction to successfully extract PHA from the bacteria. Dosage of substrate is sodium acetate piped from egg-diluted solution at 600 mg per dosage. In order for the dosage to be added at the right time, DO and the pH of the reactors were measured and logged throughout the course. FT-IR is used to view the course of events during the experimental period, linked to known features that may indicate that PHA is present in the bio sludge. Nutrients like phosphorus and nitrogen are measured, along with SÄ, SS, TOC, several before and after the experiment to compile discussion of the results.

The conclusion was based on the analysis methods that the bio sludge that yielded the best yield was from Gruvöns use. This also relates best to the hypothesis of celebration and starvation, the relationship to which the bio sludge is exposed. The mine has a slurry in its five-step process which causes the bio sludge to return from step five where there is a shortage of food for bacteria to step three where there is a lot of food to consume. The rankings of the different uses relate to the hypothesis that the use of mining was best and the worst was the use of Bäckhammar. Based on the analysis methods included in the study, it can be concluded that the bio sludge that yielded the best yield was Gruvöns use with 13.6% of PHA / VS from the soxhlet extraction, the practice was best matched to the hypothesis. The ranking of the different bio sludge of the use is based on the hypothesis that Skoghall's use was second best followed by Bäckhammar's use which was the worst in accumulating PHA in the bacterial culture.

In 2012, 30% of the total energy consumption was used by apartments and buildings. Heating of apartment buildings and commercial buildings represents 60% (79.5 TWh) of that energy consumption. There is thus great potential for reducing energy use in the residential sector. Part of the overall efficiency work is to review the control of heating systems. Today's control often involves simple on / off systems where an upper and lower limit controls when to start and stop a process. This form of control is therefore best suited to systems where the change of state occurs quickly. When it comes to homes with high mass however, it takes time before a change takes effect. In some cases, it can take up to 24h before a change is noticed for buildings with high thermal inertia. An alternative to the traditional temperature based control is the so-called MPC controller which stands for Model Predictive Control. MPC is a control method that can take into account the thermal inertia and the dynamics of buildings. MPC controller also controls the system proactive rather than retroactive, which is the technique most of current control methods use. One problem with the MPC controller thou is that it requires large computational resources and technical knowledge of the building where it will be implemented. The aim of the thesis was to design a simple MPC controller and evaluate its performance. This was done by constructing a bench test model that can evaluate the function of the MPC controller. In addition to constructing a simple MPC-controller, a study has been done on how the current control method can be more energy efficient without having to invest in new equipment. The goal was to reduce the variations in indoor temperature and improve operating economics of the building. The study was conducted at Karlstad Bostads Aktiebolag (KBAB) that owns and manages 7,300 apartments in Karlstad. The Bench test model calculated indoor temperature using the weather conditions as solar radiation, cloud cover, outside temperature and wind speed. The study presents a number of simple MPC controllers that can be used to minimize indoor temperature variations and improving operating economy. It is estimated, however, that the MPC controller that only takes into account the outside temperature in its prediction is the most appropriate. The MPC controller has the potential to reduce heating requirements by 3.12 MWh (-4%) and reduce indoor temperature variations with 96%. The mean annual temperature would be 21.1 ° C and the energy consumption 113 kWh/m2 for the building. The study also presents an alternative to current control method that does not require any additional resources or investments. It has the potential to reduce heating requirements by 8.3 MWh (10%) and reduce indoor temperature variations by 65%. The energy consumption would then be 106 kWh/m2.

Every day people buy fruit and vegetables. A problem with these produces is that they are usually not locally grown, but they have often undergone long journeys. Because fruit is perishable, they easily become damaged and rot during a long transport. The most cost effective way to extend the shelf life of fruit is by cooling it. Since it is desirable that fruits are in the same state as if they were freshly harvested, it is important that they are cooled to their optimum temperature as quickly as possible after they have been harvested. The most common pre-cooling method is forced air cooling.

The work has been done in collaboration with Billerud Fresh Services AB. The company's goal is to reduce wastage of fruits and vegetables through improved packaging solutions, with paper as raw material, thereby improving both the economic and environmental efficiency throughout the value chain, from harvesting and cooling until the fruit is on the store shelf.

The purpose of this study is to investigate what effects the use of electricity in forced-air cooling and how it can be reduced. If the energy use during the air-cooling could be reduced, then carbon emissions and economical cost of the cooling process can be reduced. This allows growers to be able to afford a complete cooling process and the losses from fruit that has been damaged due to bad cooling will decrease. This increases the value of the fruit value chain and suppresses the increase of greenhouse gases.

The aim of this study is to describe how the cooling homogeneity and the fan energy power during forced air cooling of fruits and vegetables depends on the box and the California Tunnel design.

By simulations in COMSOL Multiphysics 4.3, the impact of the vent hole ratio on the pressure drop is studied. Simulation in COMSOL has also been made to estimate how the flow varies between boxes in a California Tunnel and how this tunnel can be modified to provide a more homogeneous cooling. Experiments have been conducted to compare the cooling homogeneity in an existing box and a new box designed to create a uniform air flow.

The results of the experiment showed that the cooling homogeneity could be increased by changing the box design, thereby reducing electricity consumption. The simulation of the California tunnel showed that a modified tunnel arrangement could reduce the airflow difference between the boxes from that at a classic arrangement being 60 % to be less than 1 %. This allows the homogeneity to increase and electricity can be saved. The results of the simulations showed that if the vent hole ratio is halved, the fan energy demand will increase fourfold. Therefore it is important that, when designing a box, the vent hole ratio is high for electricity use to become low.

23.

Carlaby, Jesper

Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.

Noise from the ventilation systems affects us more or less every day. There are some requirements on how much noise that’s allowed to generate from the ventilation system set by Karlstads Kommun based on Boverkets Byggregler. But how could a more silent system be constructed at a more stringent level of requirements?

The aim is to investigate a reasonable sound level based on technology and economics. Based on Råtorps preschool, owned and operated by Karlstads Kommun, performed calculations using the existing calculation template and sound measurement according to a Swedish Standard. It is done to find out how the sound environment of preschool looks like today in relation to the requirements set. An analyze of the staff's perception of sound generation from ventilation to be able to consider what is an acceptable noise level. Subsequently, calculations are made to find out which theoretical improvements that can be done, especially technically and also financially, in order to reduce the noise level.

According to the noise measurements that are made, the noise level at the preschool is below or at the same level as the requirements. The results are consistent with the calculations performed in addition to the room that previously was in line with the requirements, now is over the limit. The noise from the ventilation is perceived as disruptive in two of the four rooms, but the results of the theoretical improvements are showing that it is possible to reduce the noise to a more acceptable level. This can be done without major financial consequences, than the most costly and improvement measure that was tested found to be least effective in lowering the noise level.

This work results in that even though the set requirements are followed as perceived ventilation to some extent as disturbing nonetheless. It would be possible to reduce noise generation with relatively small funds without excessive economic consequences and thus create a better working environment.

Heat transfer is an important physical phenomenon with many different industrial applications, where the transport of a fluid in a pipe is an important part. The main mechanism of heat transfer in flowing or stagnant fluids is convection. A better knowledge and understanding of the underlying physics would imply that the design of the systems could be optimized in order to obtain an economic process by minimizing energy losses and cost of materials.

A steam turbine in a power plant produces electricity by superheated steam flowing through the turbine. The superheated steam is then transported from the turbine into a pipeline to be used for heating processes in a nearby pulp mill. In this work, an energy analysis was carried out on the pipeline with superheated steam in order to determine the temperature distribution. The choice of material in the pipeline is dependent on pressure and temperature, and with a lack of knowledge of the temperature distribution along the pipe, the construction could be unnecessarily costly.

A mathematical model was set up with the energy balances acting on the pipeline. An analytical calculation was carried out to analyze how much the heat loss from the pipe is and how much the temperature of the steam decreases. A dynamic model was then built in Simulink to simulate the accumulation of heat in the pipe and the insulation over time, and the mass flow of cooling water. A literature study of the vaporization of the cooling water was carried out to find the parameters that affect evaporation and thus is important in determining the time it takes until all have vaporized.

The results of the calculations show that the temperature drop of the superheated steam in the flow direction becomes very small. This is because the energy content of the flowing steam is very large compared to the heat loss through the pipe wall. The result from the dynamic simulation shows that the insulation has a larger time constant compared to steel pipe. This is presented in the form of the step response.

The choice of material will be affected by the position of the desuperheater. In this system the desuperheater is not optimally placed since it is about 42 m after the inlet of the turbine. It would therefore be possible to place it closer to the turbine and then switch to a cheaper lower strength material.

Energy is a hot topic in today's society. Both businesses and individuals are trying to reduce their spending costs by saving kWh. There are many various saving measures to reduce energy consumption. Reducing energy consumption leads to a reduced carbon footprint as less fuel is burned in facilities that generate emissions. This report will focus on heat pumps, solar technologies and interventions in the building envelope for a multi-dwelling house.

How much energy can be saved from a measure? What impact does it have on the climate? Is it economically viable to invest in the measure? These issues are of importance both for the investor and future generations. In the report, these questions are answered and applied in a multi-dwelling house in Karlstad built in the 1960's with an energy consumption of 129 kWh/m2 and year. The study is a collaboration with HSB.

The building was recreated in a simulation program, VIP-Energy, for a basic case to start from. Then the measure were simulated both individually and in combination to see how effective they are in the building. These measures may lead to an increased electricity consumption, which was taken into account in the calculations of the climate impact if it led to an increased or decreased amount of CO2 emissions. All these measures are designed to reduce energy consumption, leading to a decrease in energy cost.

The results showed that these measures lead to a saving of energy consumption in all cases. The resulting reduction in energy consumption varies between 5-50% on the various measures individually, but the savings do not differ as much. The reason for this is the technical lifetime of the measures, which means that the total savings do not reflect the reduction in energy savings. Reduced CO2-emissions is much more difficult when the building is connected to a district heating plant that also produces electricity, known as a combined heat and power plant, which makes the reduced heat generation leads to reduced power generation. This means that the electricity has to be generated from another source, for Sweden this means imports of electricity from a coal condensing power plant. Electricity from the power plant is in this case CO2-compensated, which means that the fuel comes from a renewable source. In order to have reduced CO2-emissions, it requires that you have your own production of electricity from CO2-compensated or renewable sources.

Energy issues are a priority in today's society and will probably be for many years to come. In order to achieve progress in this struggle towards a more energy efficient world, global optimizations will be needed and new ways of thinking need to be realized.

In the food industry, there is great potential for optimizations and new ways of thinking. One problem area is that many grocery stores do not open their refrigerators and freezers and clean them internally, they only clean the visible surfaces. Failure to clean inside refrigerated display may cause the burdening and dirt into the system that is adversely affected. These may include impacts on the cooling coil, reducing air flow and clog the drains. Impacts on the cooling coil and the air flow in turn could lead to the destruction of food due to high temperatures in refrigerators and freezers. Clogged drains can lead to water leakage, which then can run out on the shop floor.

During this project, optimization efforts have been made and these include cleaning the cooling coils inside the refrigerator and freezer cabinets and degassing of the brine. The cleaning has been done with overheated steam to remove any burdening to the cooling coils and fans, and all surfaces in refrigerators and freezers. This has been done to see if energy can be saved by increasing the thermal conductivity of the cooling coil.

The tests that have been done to see if it is possible to save energy by cleaning are ampere- , flow- and temperature measurement.

Degassing of the coolant has been made on the basis of the same theory as cleaning. By degassing where the ambition that the brine could pick up more veil and thus increase the efficiency of the cooling system.

Degassing the coolant provides improvements in the sustainability of the system with a reduced risk of corrosion, but what happens to the heat transfer capability is relatively unknown, it has been studied through power measurements on chiller compressor.

After the test period the results of cleaning tests show that the power demand goes down, while degassing not had any impact. Degassing showed no efficiency of the system because the oxygen levels remained high.

The building sector is responsible for almost a quarter of the total carbon dioxide emissions. The urgency to reduce the emissions is reflected in the stricter guidelines which have been set all over the world. To reduce the building sector’s emissions the energy consumption need to be reduced, which can be done in two ways: building new energy efficient buildings or retrofitting of current buildings. Due to the life expectancy of current building stock the largest savings before 2030 will be made through retrofits. For this reliable computational tools are required, and currently there is a gap between the predicted and actual performance of retrofitted buildings. This thesis is going to look into how the computational method is contributing to the performance gap. A building at the RMIT campus in Melbourne, Australia, which is going to be retrofitted through retrofits designed by Siemens, is used. A thermal simulation model of the building was built, and tuned to reflect the pre-retrofit building, and compared against the measured energy performance of the building. The retrofits were then implemented in the simulation model and the gap in the predictions between the simpler computational method used by Siemens in designing the retrofits, and the extensive simulation model was compared. The gap between the computational methods were analysed in order to see how Siemens calculation method contribute to the performance gap. The conclusions which have been drawn are that the simulation model is reflecting the energy use of the building well considering the access of data available during the study. Especially the electricity use is reflected well both in the total annual use, approximately 4 % gap to measured value, and the monthly variation over the year. The total natural gas use is under predicting the annual use, approximately 40 % gap to the measured value, but shows a good correlation to the monthly variation. The electricity use is relatively stable in the simulation model, where the natural gas was sensitive for direct changes to the heating system. The input parameters which have the largest impact in the electricity use are internal gain profiles and the electrical internal gains energy use. Siemens calculation method are contributing to the performance gap through the lack of interaction between the different retrofits, the light retrofit have a noticeable impact on the heating and cooling system of the building. To only use one single period in the regression models can also easily lead to incorrect predictions. The strength of the simulation model is its ability to see the retrofits influence on each other and the possibility for scenario analysis.

33.

Eriksson, Sebastian

Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.

The reduced availability of fossil fuels and the increasing energy demand in the world creates a need to develop solutions that are financial and environment sustainable. Biofuels has grown to become one of the most important renewable energy sources in the target towards a carbon neutral society. Although the high moisture content ranging between 50-150% for unprocessed biofuels causes problems. As a result, there is a drying demand that has to be solved in an energy efficient and environmental friendly way. As of today, the drying of biomaterials pre pelletizing stands for 25 % of the total cost in pellets production.

The cost to dry biomaterials makes it important to improve the efficiency of the drying process. Simultaneously the drying process causes emissions of hazardous substances such as terpenes. The drying must also in a consistent quality so that the biomaterial is made to hold constant and uniform moisture content to enable efficient processing. Depending on the usage of the biomaterial, there is a different demand of the final moisture content before processing. The ideal moisture content for combustion for example ranges between 15-25 %, while pyrolysis would rather have moisture content between 5-10 % for effective and high quality processing. The ideal moisture content pre pelletizing is between the two mentioned processes, namely 8-12 %. Three common dryers used to dry biomaterials are rotary dryers, conveyor dryer and pneumatic dryer.

In this thesis the pressure drop in a pneumatic dryer is predicted. A pneumatic dryer a airflow simultaneously conveys and dries the wet material. Perks of a pneumatic dryer is the short amount of time required to dry the material, and simultaneously deliver uniform moisture content. The short time required also contributes to minimize the emissions of volatile organic compounds (VOC) like terpenes compared to the other two mentioned types of dryers and the risk of fire during the drying process. Although because of the high airflow compared to the material flow, pneumatic drying is costly and has difficulties with separating the dried material from the airflow.

A model to predict the pressure drop in a pneumatic dryer was created. The simulated pressure drop was then verified against a practically measured pressure drop for a pneumatic dryer. In this way a model was created to examine the pressure drop for a variety of material- and airflows. The thesis suggests how to calculate the pressure drop and velocities for the accelerating region, steady state and U-bend of pneumatic conveying. To better predict the pressure drop according to the actually measured pressure drop a correction equation was presented.

The results of the model are consistent with the research in pneumatic conveying and drying. The model gave with the usage of the correction equation a very good prediction on how the pressure drop varied over the length of the pneumatic conveying. The pressure drop was as expected larger as the airflow or material flow increased. As the sawdust accelerated on 0,4-0,6 meters there is required more points of measurements in the region between 0-0,6 meters to better establish exactly how the pressure drop in the accelerating region varies. The difference between the practically measured and the simulated pressure drop was never exceeded 7,0 % for the different flows investigated in this thesis. When disregarding the measure point at 0,4 meters the difference between measured and simulated pressure drop never exceeded 4,4 %. If one would include the heat transfer between the material- and airflow, the model could be used to predict the energy consumption and required length to achieve desired moisture content on the material.

The world agrees that humans causes negative climate changes. Combustion of fuels releases greenhouse gases. These gases contribute to heftier changes of the weather, flooding and expanding deserts. By reducing emissions of greenhouse gases climate change can be slowed down. That demands effective usage of fuel resources. District heating is a well-established system for heating up housing and water, where combustion of fuels is the source of energy. Year 2017 Trollhättan Energi AB (TEAB) produced 368 GWh district heat. The company has transitioned to rely mainly on wood chips and biooil, two renewable sources of energy. Now there is also an interest in operational improvements of their heat plants.

This study investigates time periods where biooil could have been replaced by wood chips. Wood chip is the cheaper fuel; therefore, it is of interest to increase its share of the heat production. If that’s achieved, TEAB can keep offering customers lower-priced district heating. With data from 2015–2017 a model based on linear programming was developed in MATLAB. The results from the model and analyzes of data were used to develop new operational strategies. Differences in emissions and operations costs between the data and the model during the observed time periods are presented as well.

The results show that most of the observed time periods could have been covered with the help of solid fuel boilers and the energy storage tank. This could have been accomplished through:

Co-operating more than one solid fuel boiler during time periods with a lower heat demand (<68,3 MW)

Using Stallbacka P4 (StbP4) and Kronogården P3 (KronoP3) more since their operating costs are low and they can run on relatively low effect compared to Stallbacka P3 (StbP3) and Lextorp P4 (LexP4)

Prioritizing loading up the energy storage tank before shutting down a solid fuel boiler, provided it is not fully loaded

The smaller solid fuel boilers, KronoP3 and StbP4, co-operate well in pairs with the larger solid fuel boilers, StbP3 and LexP4. Especially during time periods where one large solid fuel boiler is not enough to cover peak loads.

During the study it has been observed that the maximum effect of the boilers is rarely achieved, and that the energy storage tank is not emptied during several time periods. If the operations team becomes more consequent in achieving high effect output from the boilers and emptying the energy storage tank completely the usage of biooil can be reduced.

To achieve the solutions suggested with the model, a tool for predictions that gives prognoses of the heat demand could be handy. The tool developed in this study shows potential, despite the low amount of time and resources put into it. The most important is to test the tool and actively integrate it in production planning routines.

The solutions presented show a potential of saving 2 Mkr during 2015–2017 if the suggested operating strategies would have been adapted. The model did not calculate positive economical outcomes for all of the observed time periods. This encourage a study with a widened time-perspective covering a full year of operations. The size of the potential economical saving is considered to be low, around 0,75 % of the total operations cost for 2015–2017. The solutions do not require an investment which could increase the incentives to review the operations and production planning as it is of today.

With a lower amount of biooil and an increased amount of wood chips, the emissions of CO2-eq, CO and NOx would have potentially increased during the examined years. A deeper analysis of these emissions is suggested to determine the effects of increased emissions. If the emissions levels of NOx exceed a certain value, TEAB could be required to pay extra fees for these emissions, which lowers the profitability.

The model has potential for improvements and more areas of use. The opinion after the study is that together with prediction tools, the production planning can be made easier. With a prediction tool, new ideas of operations can be developed, tested in advance and also include more operating hours.

The energy use in a workshop company has been examined in this work in order to find areas for energy efficiency improvement. The combined oil and electricity heating in the company were compared with other alternative heating systems including cooling of the premises in following combinations:

Ground source heat pump for heating and cooling

District heating and absorption cooling

District heating and low temperate surface water cooling

Energy use, operation costs and carbon dioxide emissions were calculated for the current heating systems and the three alternatives including cooling. The ground source heat pump for heating and cooling decreases bought energy with 34 MWh annually compared to current heating only. The district heating and low temperate surface water cooling has the largest reduction of operation cost and carbon dioxide. The operation cost decreases with 42 kSEK and the carbon dioxide with 43 metric ton CO2 annually. The differences between the alternatives were smaller concerning the operation costs. The ground source heat pump alternative had smaller reductions of carbon dioxide than the other two alternatives with district heating.

An alternative heating and cooling system can also lead to alternative energy use. The choice is between electrical or heat energy. A weighting can be done to evaluate the energy use for heating on basis of how much energy is needed in order to generate the energy the end user buys. A 2.5 factor for electrical energy entails the alternative with district heating and low temperate surface water cooling gets the lowest heating and cooling energy in comparison.

An inventory of the lighting was also done. The company has already an energy effective lighting but yet another saving of 2 MWh can be done annually without replacement of armatures.

Finally, the operation time of the compressor was calculated with a mean value of 11 hours per day. The compressor delivers pressure air to machines and tools. There can be a great demand for pressure air in the workshop but the operation time can also be an indication of leakage in the air net.

The use of wood fuel pellets has increased worldwide in recent years, and pellet producers conclude that the lack of drying capacity is a barrier to increased production. In this study, we develop a concept of two different dryers called the two-step drying technique. The aim is to show the potential for increasing the drying capacity and improving energy efficiency when introducing a second dryer into the pellet plant. The study is theoretical and based on an industrial packed moving bed dryer. It shows that the drying capacity increased by 22% when a pneumatic second dryer was used.

The sun is a huge energy source with great potential of providing energy to the heating of homes and other buildings in an environmentally sustainable manner. In order to provide buildings with energy from the sun it is necessary to transfer the energy supply over time to when the demand arises. By storing the heat in a seasonal storage, solar energy from the summer can be used in the winter when the demand for heating is greatest.

Today's existing plants are mainly in Europe and particularly in Germany. These facilities are designed to supply heat demands greater than 400 MWh and covers about 40-50 % of this need which consists of energy for space heating and domestic hot water. How much of the heat demand that is covered, the solar fraction, is partly due to losses from the storage which in turn is connected to the surface area of the storage. The bigger a storage, the smaller the losses because of the decreasing relationship between surface area and storage volume. Looking at the size of the seasonal storages that are currently in operation, the question if seasonal storage is also suitable for installations designed for heat demands smaller than 400 MWh arises.

Jonas Haglund at the architect office Skanark AB in Karlstad is planning an accommodation of 40 flats and hopes that seasonal stored solar energy can serve as the main energy source for space heating and hot water. In order to make housing more attractive he is considering the idea of adding other features, like a pool and an atrium, that also require heating but with lower temperature requirements. Haglund would like to investigate whether the efficiency of the solar collector increases when the extra energy demands are added and if the energy cost, for those demands, in this way can be reduced.

The purpose of this study is to investigate the possibility of covering a large fraction of a small-scale annual heat demand corresponding to about 40 newly built apartments. The study shall present the solar fractions that can be achieved with different storage concepts when storage size and collector area is varied. The study will also answer how the solar fraction will change if a heating demand with lower temperature requirements and varied character is added to the basic domestic heating and if the added energy demand to some extent can be free. These questions are answered by calculations and simulations with the simulation software COMSOL Multiphysics.

The results show that it is possible to obtain solar fractions above 80% with sufficient collector area. Suitable storage volume varies depending on the specific storage concept. Simulations of seasonal storage in a tank show that a storage volume of 13 m3/MWh is an appropriate size, while the corresponding figure for duct storage in clay is 20 m3/MWh. An added heating demand of low temperature character increases the efficiency of the solar panels and creates, so called, free energy.

Sweden stands today with major challenges to reduce the impact on the climate and the environment. A big part of managing to achieve a sustainable society is to reduce energy consumption. Today the industry accounts for one third of Sweden's energy consumption and in the steel industry, there is great potential to make energy savings.

There are around hundred steel mills in Sweden and these produce a large amount of steel every year. In the manufacturing process, when the steel is tapped into ladles there is formed at thin layer of unwanted residue on the top of the ladle. This product is called slag. The residue product that is not used is scraped to a slag ladle. When this process is performed, follows steel of finer quality in to the ladle. The finer the quality of the steel burns a hole in the slag ladles that can be about 300-500 millimetres in diameter.

With the current technology, are the slag ladles repaired using MIG/MAG welding. This method is well established in the steel industries. The method is a rather slow process of welding, the techniques must sit and the repairing takes about five weeks. The process is both inefficient, energy- intensive and expensive. Which also results in a big impact on the climate and the environment.

Thomas Lindberg is an inventor who had an idea. All repair and splicing of railway track using a method called Termite welding. The method applies a composition of iron and aluminium powder is heated and forms a volume of molten metal in a short time. Thomas thought that this method would be well suited to the repair slag ladles in the steel industries. The method works well and there have been thoughts that the method has significant advantages over MIG/MAG welding.

Therefore, these two methods were compared regarding of the time consumption, energy consumption and energy costs.

To analyze the methods there were interviews including welding techniques and the calculations was based on a general steel mill in Sweden.

The study showed that the Lindberg method was is a good alternative to MIG/MAG welding with better characteristics regarding; time consumption, energy consumption and energy costs.

Continued increase in carbon dioxide emissions lead the ecosystems towards rapid, dangerous and irreversible climate change. The Swedish forest industry is an important operator to satisfy the future demand of renewable bio products to reduce the use of fossil fuels. The increase in production means increased pressure on the Swedish forests. Society, government, companies and individuals have a responsibility to secure that the harvesting of forests remains sustainable.

The wastewater treatment plants in the pulp and paper industry produce a large proportion of biomass, in form of bio and fiber sludge. Bio and fiber sludge contains nutrients that can be returned to the forest. The upgrade of biomass to pyro-char has proven properties that improve the fertility of the forest, primarily by increasing the soil's pH value. Pyro-char improves the retention of nutrients in the soil by cation adsorption, which affects the trees and plant growth. The composition of the soil changes as pyro-char is added, and the change in composition affects the biodiversity in ecosystems. The biofuel ash extracted from the heating boilers in the paper industry contains basic cations and alkaline pH, which counteracts acidification in forest land.

The disadvantage of biomass is the high bulk density, which affects the logistics of transport and storage. There are methods for solving the problems in logistics, for example compression. Compression is a well-proven method for upgrading the biomass to pellets and improving the physical properties of the biomass. The conversion of biomass into pellets increases the density, mechanical strength and the moisture absorption capacity decreases. Pelletizing biomass results in a homogeneous product can be created and delivered as pellets.

The purpose of this study is to increase the knowledge on how lignin as an additive, and how mechanical force affects the physical properties of the nutritional pellets. The production of nutrition pellets consists of two stages, a preliminary investigation and a test matrix. The purpose of the preliminary study is to acquire guideline values ​​and provide a basis for the experimental matrix. The experimental matrix is ​​a continued study of how lignin content and pressure affect the physical properties of the nutrition pellet. The lignin content that was analyzed was 5-20 % with mechanical force that varied between 5, 10 and 15 kN. The nutritional pellets are evaluated based on the properties density, hardness, pH, moisture absorption capacity and energy use.

The single-pelletizer press, located at Karlstad University, was used to pelletize the different mixtures. The pellet properties were evaluated at the laboratory at Karlstad University.

The result shows that the test series with a pressure of 15 kN and the lignin content of 20% resulted in the highest density, hardness, moisture absorption capacity and the second highest energy consumption. Depending on the mechanical force and lignin content used, the parameters varied as follows.

The density varies between 843.5 – 1,054 kg/m3

The hardness ranged between <1 and 3.7 kg

The moisture content of the pellets varied between 8.7% and 9.2% after 96 hours

The pH-value varied between 8.7-9.58 after 24 hours and decreased between 2- 4.9 % after 48 hours

Intergovernmental Panel on Climate Change, IPCC finds that the conditions for life on Earth are changing and that this change derives most likely to humans. The consequences claimed by other successful research initiatives to be of such magnitude that it is justified to speak of a new geological epoch, the Anthropocene. A significant driver of this change are human emissions of greenhouse gases, which to the part can be attributed to an electricity need. Photovoltaic is a technology with which electricity can be produced with significantly less greenhouse gas emissions than conventional techniques. The expansion of solar energy is thus a desirable environmental measure. The profitability of solar electricity has been an obstacle for the expansion, in particular for commercial establishments. In a sensitivity analysis performed in a study from 2014 which examines the profitability of photovoltaic (PV) plants in Sweden shows that the estimated production of electricity in the first year is the factor, second only to the initial investment cost, which has the greatest impact on the profitability calculations. In calculating the PV electricity different methods with different accuracy are used. The most accurate method involves the use of commercial software packages like PVsyst, Polysun, and PV * SOL. In a study from 2014 the accuracy of some of the above mentioned program packages was compared and notes a discrepancy in the order of seven to nine percent. According to the same report, the majority of this miscalculated power generation is attributable to the solar cell model. The solar cell model is the part of the software packages that simulate the solar cell power generation based on values of solar radiation and the solar cell temperature. There are several different solar cell models, some of which are claimed to be more accurate than others. The software package that is likely to be the most prevalent in the planning of photovoltaic plants, PVsyst, does not use the variant of the solar cell model that is claimed to be the most accurate. This thesis investigates how the implementation of a novel and more accurate solar cell model in PVsyst would affect the profitability calculations for commercial PV plants in Sweden. The work can be divided into two parts, where the first part generates input data to the other. In the first part, the more accurate solar cell model and the solar cell model that can be found in PVsyst are programmed in MATLAB. The accuracy of reconstruction of power generation based on measurement data is calculated and the difference between the solar cell models are input to the second part of the work, the profitability calculations. The profitability calculations in this work springs from the outer conditions identified for a real case where the interested party consists of a non - private operator with a ground area available for a solar installation. The results show that the new solar cell model is two percent more carefully when calculating the electricity generation, which corresponds in order of a quarter of the total discrepancy of prediction tool PVsyst. This does not strike through in the profitability calculation to any significant extent but would the whole discrepancy be eliminated it would allow the use of a discount rate increased by about half a percent. The work also shows that commercial photovoltaic systems today can be profitable. A positive net present value was calculated based on a discount rate of five percent for a fix installation that cover the whole area.

Residues from forest-industry wastewater-treatment systems are treated as waste at many pulp and paper mills. These organic substances have previously been shown to have potential for production of large quantities of biogas. There is concern, however, that the process would require expensive equipment because of the slow degradation of these substances. Pure non-fibrous sludge from forest industry showed lower specific methane production during mesophilic digestion for 19 days, 53 ± 26 Nml/g of volatile solids as compared to municipal sewage sludge, 84 ± 24 Nml/g of volatile solids. This paper explores the possibility of using anaerobic co-digestion with municipal sewage sludge to enhance the potential of methane production from secondary sludge from a pulp and paper mill. It was seen in a batch anaerobicdigestion operation of 19 days that the specific methane production remained largely the same for municipal sewage sludge when up to 50% of the volatile solids were replaced with forest-industry secondary sludge. It was also shown that the solid residue from anaerobic digestion of the forest-industry sludge should be of suitable quality to use for improving soil quality on lands that are not used for food production.

45.

Hagelqvist, Alina

Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.

Forest industries produce large amounts of carbon rich sludges as by-products in their processes. Presently sludge is treated as a poor quality biofuel for co-incineration, some mills treat it solely as a disposal problem. This thesis provides an introduction to production, composition and disposal issues of sludge. It also includes a presentation of strategies for sludge handling.

The main concern with energy recovery from sludge is connected to high content of water (50-80%). Mechanical dewatering is an energy efficient method of decreasing the water content. However, there are limitations to how far sludge can be dewatered mechanically. Thermal dewatering is sometimes required to dewater the sludge beyond these limits, in order to obtain a high quality biofuel for incineration and/or thermal gasification. It is often inefficient, from an energy point of view, to incorporate thermal dewatering in the sludge handling strategy.

An interesting alternative to thermal processes is anaerobic digestion, which is a biological process used for energy recovery. Advantages with anaerobic digestion include biogas production, efficient treatment of sludge with high content of water and potential for nutrients recovery. The process and the kinetics of anaerobic digestion are presented.

The aim of this thesis is to present a method for evaluating different sludge handling strategies from an energy perspective, and to further develop anaerobic digestion as a process for energy recovery from sludge. The thesis is based on two papers. Paper I presents an inclusive approach with focus on energy use and energy recovery in wastewater management, including wastewater treatment and sludge handling. Paper II explores the possibility to enhance biogas production by anaerobic co-digestion of pulp mill sludge with municipal sewage sludge.

The production of pulp and paper is associated with the generation of large quantities of wastewater that has to be purified to avoid severe pollution of the environment. Wastewater purification in pulp and paper mills combines sedimentation, biological treatment, chemical precipitation, flotation and anaerobic treatment, and the specific combination of techniques is determined by the local conditions. Wastewater treatment generates large volumes of sludge that after dewatering can be incinerated and thus used for bio-energy production. Sludge is currently viewed as biofuel of poor quality due to its high water content, and some mills treat it solely as a disposal problem.

Two strategies have been identified as feasible options to improve the energy efficiency of sludge management. One is drying using multi-effect evaporation followed by incineration. The other is anaerobic digestion of the wet sludge to produce methane.

This thesis explores the energy balances of sludge management strategies in pulp and paper mills with special focus on anaerobic digestion. The first part consists of a system analysis, used to evaluate some wastewater treatment processes and sludge management, and the second part of empirical studies of anaerobic digestion of pulp and paper mill sludge. It was shown that the use of energy for aeration in aerobic biological treatment should be kept to the minimum required for acceptable quality of the processed water. Additional aeration for reduction of the generated sludge will only result in reduced energy generation in a subsequent methane generation stage. In the second part of the thesis, it is shown that anaerobic digestion is a feasible option for sludge management as it leads to production of high value biogas. Co-digestion with grass silage, cow/pig manure or municipal sewage sludge should then be used to counteract the low nitrogen content of pulp and paper mill sludge.

The purpose of this research is to evaluate how methane production is affected by the co-digestion of pig and dairy manure with grass silage and pulp and paper mill sludge at mesophilic conditions, and to assess whether methane production is affected by other factors than the now known ones, i.e., nutrient deficiency, low buffering capacity, inadequate dilution, and an insufficient activity and amount of microorganism culture. The season of grass silage and manure collection proved to be an important, previously unreported, factor affecting short-term (20 days) methane production.

Sludge formed during the necessary wastewater treatment in forest industry is currently considered to be a waste stream; rich in organic substances and poor in macronutrients, especially phosphorus and nitrogen. Previous work has shown that excessive use of electricity for aeration in wastewater treatment counteracts the potential for energy recovery in the subsequent sludge handling system, as prolonged aeration is used to degrade organic matter. This work shows that chemical oxygen demand of wastewater was not reduced further when the solids retention time was increased in aerated wastewater treatment from 2 days to 10 and 20 days respectively. The results presented here strengthen the previous conclusion that energy should only be used for sufficient effluent treatment, not for sludge reduction. A decreased need for aeration can be achieved by shortening the sludge retention time both by a decreased oxygen requirement and increased aeration efficiency. Shortened sludge retention time was shown here to increase production of biosludge as well as to increase the specific methane potential of biosludge. The results show that sludge with shorter solids retention time in the aerated treatment step gives more production of methane gas compared to sludge with longer solids retention time.

The aim of this study was to find a way to shorten the start-up time of a pig and dairy manure based anaerobic digester without addition of external inoculum. Self-degradation was tested to simulate the setting of many sites where the use of external seed culture is not feasible because of the large distance to a nearest location where appropriate material can be collected. In this case study, co-digestion of pig and dairy manure with grass silage and pulp and paper mill sludge was tested using different compositions. The results showed that one tertiary mixture of 17 per cent of piggery manure, 17 per cent of dairy manure and 66 per cent of pulp and paper mill sludge resulted in a considerably shorter start-up time (about 15 days) as well as in a higher methane yield (120 ml CH4/g VS added after 44 days of batch operation) as compared to other mixtures tested. This mixture composition is recommended to start-up the full-scale process. Concentrations of ammonium of 0.4 g/l combined with slowly degradable material favoured a rapid start and efficient digestion.

The gas turbine has an important role for the energy distribution due to its stability and flexibility. By increasing turbine inlet temperature (TIT) an increased thermal efficiency of the turbine can be achieved. The biggest limitation of the TIT is the material of the turbine components. To avoid this limitation, cooling is needed in the first stages of the turbine by air from the compressor. The downside of the cooling is the decrease of efficiency with excess of cooling air. To achieve an optimum cooling flow, the designing process is important. One major tool in the designing process is simulations by Computational Fluid Dynamics (CFD).

For optimum and correct cooling design, the CFD simulations needs to accurate predict the temperature transport through the turbine. Therefore, this study focused to estimate the accuracy of different CFD methods in predicting the temperature distribution through a 1.5 stage turbine with experimental results. The CFD simulations were done by using Ansys CFX and divided into two study cases with steady RANS. One with different turbulence models; –, Wilcox – and SST – . The other with two different simulation approaches of interfaces for frame change; Mixing plane and Frozen rotor. All simulations included two configurations of swirlers clocking for interest of their differences within the turbine and validation of the CFD simulations; Passage (PA) and Leading Edge (LE) clockings.

The experimental results showed a formation of gradually more uniformed temperature profile with the fluid. This could not be seen in the same extend with any of the simulations. The temperature difference between the hot and cold section with all simulations were marginally decreased in comparison of the measurements. All results with steady RANS simulations tended to over and under predict the temperatures of the hot respectively cold sections within the fluid flow through the turbine. This occurred already after the first stage guide vanes and the difference from the measurements increased after the first stage rotor. This since the steady RANS tended to under predict the mixing process through the turbine.

Differences between the turbulence models were noticeable after the rotor blades, where the – turbulence model predicted most mixing of the evaluated turbulence models but badly compared to the measurements. Another outcome from this study was that the frozen rotor interface with several positions of the rotor blades did not stated better results compared to mixing plane interface for temperature distribution in axial turbines. On the other hand, one simulation of one position of the rotor with frozen rotor interface could be used to simulate an approximatively similar circumferential average temperature as the mixing plane with better convergence with the disadvantage of bigger domain.

The gas turbine has an important role for the energy distribution due to its stability and flexibility. By increasing turbine inlet temperature (TIT) an increased thermal efficiency of the turbine can be achieved. The biggest limitation of the TIT is the material of the turbine components. To avoid this limitation, cooling is needed in the first stages of the turbine by air from the compressor. The downside of the cooling is the decrease of efficiency with excess of cooling air. To achieve an optimum cooling flow, the designing process is important. One major tool in the designing process is simulations by Computational Fluid Dynamics (CFD).

For optimum and correct cooling design, the CFD simulations needs to accurate predict the temperature transport through the turbine. Therefore, this study focused to estimate the accuracy of different CFD methods in predicting the temperature distribution through a 1.5 stage turbine with experimental results. The CFD simulations were done by using Ansys CFX and divided into two study cases with steady RANS. One with different turbulence models; –, Wilcox – and SST – . The other with two different simulation approaches of interfaces for frame change; Mixing plane and Frozen rotor. All simulations included two configurations of swirlers clocking for interest of their differences within the turbine and validation of the CFD simulations; Passage (PA) and Leading Edge (LE) clockings.

The experimental results showed a formation of gradually more uniformed temperature profile with the fluid. This could not be seen in the same extend with any of the simulations. The temperature difference between the hot and cold section with all simulations were marginally decreased in comparison of the measurements. All results with steady RANS simulations tended to over and under predict the temperatures of the hot respectively cold sections within the fluid flow through the turbine. This occurred already after the first stage guide vanes and the difference from the measurements increased after the first stage rotor. This since the steady RANS tended to under predict the mixing process through the turbine.

Differences between the turbulence models were noticeable after the rotor blades, where the – turbulence model predicted most mixing of the evaluated turbulence models but badly compared to the measurements. Another outcome from this study was that the frozen rotor interface with several positions of the rotor blades did not stated better results compared to mixing plane interface for temperature distribution in axial turbines. On the other hand, one simulation of one position of the rotor with frozen rotor interface could be used to simulate an approximatively similar circumferential average temperature as the mixing plane with better convergence with the disadvantage of bigger domain.